The present invention relates to novel rubber-modified impact polystyrene compositions having high transparency, impact strength and heat distortion temperature properties.
While rubber-modified impact polystyrenes possess excellent impact strength properties, they do not possess the optical transparency which is desired for many use applications. The prior art has long sought to improve the optical transparency of rubber-modified impact polystyrenes without severely compromising the high impact properties which they inherently possess.
The employment of alkyl methacrylate as comonomer in the production of rubber-modified impact polystyrene has long been known. This modification, i.e., replacement of a portion of the styrene monomer with alkyl methacrylate, results in rubber-modified impact polystyrenes with improved optical transparency. However, such modification, while resulting in products having improved optical transparency and not greatly compromised impact strength properties, does result in reductions in heat distortion temperature properties.